Sulfur dioxide

Formula: O₂S
Molecular weight: 64.064
IUPAC Standard InChI: InChI=1S/O2S/c1-3-2
IUPAC Standard InChIKey: RAHZWNYVWXNFOC-UHFFFAOYSA-N
CAS Registry Number: 7446-09-5
Chemical structure:
This structure is also available as a 2d Mol file or as a computed 3d SD file
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Other names: Sulfurous acid anhydride; Fermenicide powder; Fermenticide liquid; Sulfur oxide (SO2); Sulfurous anhydride; Sulfurous oxide; SO2; Sulphur dioxide; Fermenicide liquid; Schwefeldioxyd; Siarki dwutlenek; Sulfur oxide; UN 1079; Sulfur dioxide (SO2); Sulfur superoxide
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Information on this page:
Other data available:
- Phase change data
- Reaction thermochemistry data: reactions 51 to 100, reactions 101 to 102
- Henry's Law data
- IR Spectrum
- Mass spectrum (electron ionization)
- Fluid Properties
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Gas phase thermochemistry data

Go To: Top, Reaction thermochemistry data, Gas phase ion energetics data, Ion clustering data, Gas Chromatography, References, Notes

Quantity	Value	Units	Method	Reference	Comment
Δ_fH°_gas	-70.939 ± 0.048	kcal/mol	Review	Cox, Wagman, et al., 1984	CODATA Review value
Δ_fH°_gas	-70.946	kcal/mol	Review	Chase, 1998	Data last reviewed in June, 1961
Quantity	Value	Units	Method	Reference	Comment
S°_{gas,1 bar}	59.327 ± 0.012	cal/mol*K	Review	Cox, Wagman, et al., 1984	CODATA Review value
S°_{gas,1 bar}	59.324	cal/mol*K	Review	Chase, 1998	Data last reviewed in June, 1961

Gas Phase Heat Capacity (Shomate Equation)

C_p° = A + B*t + C*t² + D*t³ + E/t²
H° − H°_298.15= A*t + B*t²/2 + C*t³/3 + D*t⁴/4 − E/t + F − H
S° = A*ln(t) + B*t + C*t²/2 + D*t³/3 − E/(2*t²) + G
C_p = heat capacity (cal/mol*K)
H° = standard enthalpy (kcal/mol)
S° = standard entropy (cal/mol*K)
t = temperature (K) / 1000.

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Temperature (K)	298. to 1200.	1200. to 6000.
A	5.122011	13.73850
B	17.77030	0.241235
C	-13.80310	-0.018234
D	3.909021	0.001237
E	0.020729	-0.966874
F	-73.08050	-77.53681
G	60.91950	72.36611
H	-70.94699	-70.94699
Reference	Chase, 1998	Chase, 1998
Comment	Data last reviewed in June, 1961	Data last reviewed in June, 1961

Reaction thermochemistry data

Go To: Top, Gas phase thermochemistry data, Gas phase ion energetics data, Ion clustering data, Gas Chromatography, References, Notes

Data compiled as indicated in comments:
B - John E. Bartmess
M - Michael M. Meot-Ner (Mautner) and Sharon G. Lias

Note: Please consider using the reaction search for this species. This page allows searching of all reactions involving this species. A general reaction search form is also available. Future versions of this site may rely on reaction search pages in place of the enumerated reaction displays seen below.

Reactions 1 to 50

+ Sulfur dioxide = ( • )

By formula: Cl^- + O₂S = (Cl^- • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	22.2 ± 2.0	kcal/mol	TDAs	Caldwell and Kebarle, 1985	gas phase; B,M
Δ_rH°	20.9 ± 2.0	kcal/mol	IMRE	Larson and McMahon, 1985	gas phase; B
Δ_rH°	22.2 ± 2.2	kcal/mol	TDEq	Bohringer, Fahey, et al., 1984	gas phase; Relative to HOH..Cl^- in Keesee, Lee, et al., 1980; B,M
Δ_rH°	21.80 ± 0.20	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B,M
Δ_rH°	20.9	kcal/mol	ICR	Larson and McMahon, 1984	gas phase; switching reaction(Cl-)t-C4H9OH, Entropy change calculated or estimated; French, Ikuta, et al., 1982; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	21.6	cal/mol*K	PHPMS	Caldwell and Kebarle, 1985	gas phase; M
Δ_rS°	24.1	cal/mol*K	N/A	Bohringer, Fahey, et al., 1984	gas phase; switching reaction(Cl-)H2O), Entropy change calculated or estimated; Keesee and Castleman, 1980; M
Δ_rS°	20.8	cal/mol*K	N/A	Larson and McMahon, 1984	gas phase; switching reaction(Cl-)t-C4H9OH, Entropy change calculated or estimated; French, Ikuta, et al., 1982; M
Δ_rS°	23.2	cal/mol*K	HPMS	Keesee, Lee, et al., 1980	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	15.7 ± 2.0	kcal/mol	TDAs	Caldwell and Kebarle, 1985	gas phase; B
Δ_rG°	14.7 ± 2.0	kcal/mol	IMRE	Larson and McMahon, 1985	gas phase; B
Δ_rG°	15.0 ± 1.6	kcal/mol	TDEq	Bohringer, Fahey, et al., 1984	gas phase; Relative to HOH..Cl^- in Keesee, Lee, et al., 1980; B,M
Δ_rG°	14.80 ± 0.30	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B
Δ_rG°	14.7	kcal/mol	ICR	Larson and McMahon, 1984	gas phase; switching reaction(Cl-)t-C4H9OH, Entropy change calculated or estimated; French, Ikuta, et al., 1982; M

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
14.2	296.	FA	Fehsenfeld and Ferguson, 1974	gas phase; switching reaction(Cl-)H2O; M

+ Sulfur dioxide = ( • )

By formula: F^- + O₂S = (F^- • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	53.8 ± 2.2	kcal/mol	CIDT	Lobring, Check, et al., 2003	gas phase; B
Δ_rH°	53.0 ± 2.5	kcal/mol	CIDT	Squires, 1992	gas phase; B
Δ_rH°	43.8	kcal/mol	ICR	Larson and McMahon, 1985	gas phase; switching reaction(F-)H2O, Entropy change calculated or estimated; Arshadi, Yamdagni, et al., 1970; M
Δ_rH°	43.8 ± 2.0	kcal/mol	IMRE	Larson and McMahon, 1983	gas phase; These relative affinities are ca. 10 kcal/mol weaker than threshold values (see Wenthold and Squires, 1995) for donors greater than ca. 27 kcal/mol in free energy. This discrepancy has not yet been resolved, though the stronger value appears preferable.; B,M
Δ_rH°	59.	kcal/mol	SAMS	Robbiani and Franklin, 1979	gas phase; Cl- + CO2ClF --> SO2F- + Cl2, Δ_rH>; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	24.	cal/mol*K	N/A	Larson and McMahon, 1985	gas phase; switching reaction(F-)H2O, Entropy change calculated or estimated; Arshadi, Yamdagni, et al., 1970; M
Δ_rS°	23.0	cal/mol*K	N/A	Larson and McMahon, 1983	gas phase; switching reaction(F-)H2O, Entropy change calculated or estimated; Arshadi, Yamdagni, et al., 1970; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	36.6	kcal/mol	ICR	Larson and McMahon, 1985	gas phase; switching reaction(F-)H2O, Entropy change calculated or estimated; Arshadi, Yamdagni, et al., 1970; M
Δ_rG°	36.9 ± 2.0	kcal/mol	IMRE	Larson and McMahon, 1983	gas phase; These relative affinities are ca. 10 kcal/mol weaker than threshold values (see Wenthold and Squires, 1995) for donors greater than ca. 27 kcal/mol in free energy. This discrepancy has not yet been resolved, though the stronger value appears preferable.; B,M

+ Sulfur dioxide = ( • )

By formula: NO₃^- + O₂S = (NO₃^- • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	17.2 ± 2.0	kcal/mol	TDEq	Bohringer, Fahey, et al., 1984	gas phase; Relative to HOH..NO₃^-, Keesee, Lee, et al., 1980; B,M
Δ_rH°	18.2 ± 1.2	kcal/mol	TDAs	Wlodek, Luczynski, et al., 1983	gas phase; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	25.2	cal/mol*K	N/A	Bohringer, Fahey, et al., 1984	gas phase; switching reaction(NO3-)H2O, Entropy change calculated or estimated; Lee, Keesee, et al., 1980; M
Δ_rS°	31.6	cal/mol*K	HPMS	Wlodek, Luczynski, et al., 1983	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	9.6 ± 2.0	kcal/mol	TDEq	Bohringer, Fahey, et al., 1984	gas phase; Relative to HOH..NO₃^-, Keesee, Lee, et al., 1980; B,M
Δ_rG°	10.00 ± 0.10	kcal/mol	TDAs	Banic and Iribarne, 1985	gas phase; B
Δ_rG°	8.80 ± 0.90	kcal/mol	TDAs	Wlodek, Luczynski, et al., 1983	gas phase; B
Δ_rG°	10.6	kcal/mol	FA	Fehsenfeld and Ferguson, 1974	gas phase; switching reaction(NO3-)SO2, Entropy change calculated or estimated; Lee, Keesee, et al., 1980; M

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
10.0	299.	HPMS	Banic and Iribarne, 1985	gas phase; electric fields; M

+ Sulfur dioxide = ( • )

By formula: I^- + O₂S = (I^- • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	14.3 ± 2.0	kcal/mol	TDAs	Caldwell and Kebarle, 1985	gas phase; B,M
Δ_rH°	12.90 ± 0.10	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	17.6	cal/mol*K	PHPMS	Caldwell and Kebarle, 1985	gas phase; M
Δ_rS°	20.2	cal/mol*K	HPMS	Keesee, Lee, et al., 1980	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	9.0 ± 2.6	kcal/mol	TDAs	Caldwell and Kebarle, 1985	gas phase; B
Δ_rG°	1.70 ± 0.10	kcal/mol	TDAs	Banic and Iribarne, 1985	gas phase; B
Δ_rG°	6.80 ± 0.20	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
9.0	301.	HPMS	Banic and Iribarne, 1985	gas phase; electric fields; M

O₂S^- + Sulfur dioxide = (O₂S^- • )

By formula: O₂S^- + O₂S = (O₂S^- • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	24.00 ± 0.20	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B,M
Δ_rH°	21.3 ± 1.3	kcal/mol	TDAs	Vacher, Leduc, et al., 1994	gas phase; B
Δ_rH°	18.50	kcal/mol	N/A	Dresch, Kramer, et al., 1991	gas phase; Both dissociation and electron detachment?; B
Δ_rH°	18.30	kcal/mol	N/A	Snodgrass, Coe, et al., 1988	gas phase; Appears to be dissociation + electron detachment; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	33.8	cal/mol*K	HPMS	Keesee, Lee, et al., 1980	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	13.90 ± 0.40	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B
Δ_rG°	10.4 ± 2.2	kcal/mol	TDAs	Vacher, Leduc, et al., 1994	gas phase; B

+ Sulfur dioxide = ( • )

By formula: NO₂^- + O₂S = (NO₂^- • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	25.90 ± 0.20	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B,M
Δ_rH°	24.3 ± 1.0	kcal/mol	TDEq	Bohringer, Fahey, et al., 1984	gas phase; Relative to HOH..NO₂^-, Keesee, Lee, et al., 1980; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	36.8	cal/mol*K	HPMS	Keesee, Lee, et al., 1980	gas phase; M
Δ_rS°	31.6	cal/mol*K	N/A	Bohringer, Fahey, et al., 1984	gas phase; switching reaction(NO2-)H2O, Entropy change calculated or estimated; Lee, Keesee, et al., 1980; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	14.90 ± 0.30	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B

CO₃^- + Sulfur dioxide = (CO₃^- • )

By formula: CO₃^- + O₂S = (CO₃^- • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	14.	kcal/mol	HPMS	Keesee, Lee, et al., 1980	gas phase; switching reaction(O-)CO2, Entropy change calculated or estimated; Fehsenfeld and Ferguson, 1974; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	20.	cal/mol*K	N/A	Keesee, Lee, et al., 1980	gas phase; switching reaction(O-)CO2, Entropy change calculated or estimated; Fehsenfeld and Ferguson, 1974; M

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
8.0	296.	HPMS	Keesee, Lee, et al., 1980	gas phase; switching reaction(O-)CO2, Entropy change calculated or estimated; Fehsenfeld and Ferguson, 1974; M

( • Sulfur dioxide ) + = ( • • )

By formula: (Cl^- • O₂S) + H₂O = (Cl^- • H₂O • O₂S)

Bond type: Hydrogen bond (negative ion to hydride)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	10.40	kcal/mol	TDAs	Upschulte, Schelling, et al., 1984	gas phase; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	19.4	cal/mol*K	HPMS	Upschulte, Schelling, et al., 1984	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	4.60	kcal/mol	TDAs	Upschulte, Schelling, et al., 1984	gas phase; B

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
5.5	296.	FA	Fehsenfeld and Ferguson, 1974	gas phase; From thermochemical cycle,switching reaction(H2O/SO2); M

( • Sulfur dioxide ) + = ( • 2)

By formula: (Cl^- • O₂S) + O₂S = (Cl^- • 2O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	12.3 ± 1.0	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B,M
Δ_rH°	12.3	kcal/mol	PHPMS	Caldwell and Kebarle, 1985	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	20.2	cal/mol*K	PHPMS	Caldwell and Kebarle, 1985	gas phase; M
Δ_rS°	22.7	cal/mol*K	HPMS	Keesee, Lee, et al., 1980	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	5.5 ± 2.2	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B

( • Sulfur dioxide ) + = ( • 2)

By formula: (NO₂^- • O₂S) + O₂S = (NO₂^- • 2O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	9.00 ± 0.20	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B,M
Δ_rH°	9.8	kcal/mol	HPMS	Wlodek, Luczynski, et al., 1983	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	21.5	cal/mol*K	HPMS	Wlodek, Luczynski, et al., 1983	gas phase; M
Δ_rS°	16.8	cal/mol*K	HPMS	Keesee, Lee, et al., 1980	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	4.00 ± 0.40	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B

( • 3 Sulfur dioxide ) + = ( • 4)

By formula: (Na⁺ • 3O₂S) + O₂S = (Na⁺ • 4O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	12.3	kcal/mol	HPMS	Castleman, Peterson, et al., 1983	gas phase; Entropy change calculated or estimated; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	27.	cal/mol*K	N/A	Castleman, Peterson, et al., 1983	gas phase; Entropy change calculated or estimated; M

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
3.2	328.	HPMS	Castleman, Peterson, et al., 1983	gas phase; Entropy change calculated or estimated; M

( • Sulfur dioxide ) + = ( • • )

By formula: (Br^- • O₂S) + HBr = (Br^- • HBr • O₂S)

Bond type: Hydrogen bond (negative ion to hydride)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	12.2	kcal/mol	PHPMS	Caldwell and Kebarle, 1985	gas phase; From thermochemical cycle,switching reaction(Br- HBr)SO2; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	19.2	cal/mol*K	PHPMS	Caldwell and Kebarle, 1985	gas phase; From thermochemical cycle,switching reaction(Br- HBr)SO2; M

( • Sulfur dioxide • ) + = ( • 2 • )

By formula: (Cl^- • O₂S • H₂O) + O₂S = (Cl^- • 2O₂S • H₂O)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	11.8	kcal/mol	HPMS	Upschulte, Schelling, et al., 1984	gas phase; From thermochemical cycle; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	26.0	cal/mol*K	HPMS	Upschulte, Schelling, et al., 1984	gas phase; From thermochemical cycle; M

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
4.1	296.	HPMS	Upschulte, Schelling, et al., 1984	gas phase; From thermochemical cycle; M

+ Sulfur dioxide = ( • )

By formula: Na⁺ + O₂S = (Na⁺ • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	18.9	kcal/mol	FA	Perry, Rowe, et al., 1980	gas phase; Entropy change calculated or estimated; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	20.3	cal/mol*K	N/A	Perry, Rowe, et al., 1980	gas phase; Entropy change calculated or estimated; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	12.8	kcal/mol	FA	Perry, Rowe, et al., 1980	gas phase; Entropy change calculated or estimated; M

( • Sulfur dioxide ) + = ( • • )

By formula: (Br^- • O₂S) + HCl = (Br^- • HCl • O₂S)

Bond type: Hydrogen bond (negative ion to hydride)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	22.4	kcal/mol	PHPMS	Caldwell and Kebarle, 1985	gas phase; From thermochemical cycle,switching reaction(Br-)SO2; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	18.6	cal/mol*K	PHPMS	Caldwell and Kebarle, 1985	gas phase; From thermochemical cycle,switching reaction(Br-)SO2; M

( • 2) + Sulfur dioxide = ( • • 2)

By formula: (Cl^- • 2H₂O) + O₂S = (Cl^- • O₂S • 2H₂O)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	14.1	kcal/mol	HPMS	Upschulte, Schelling, et al., 1984	gas phase; From thermochemical cycle; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	19.4	cal/mol*K	HPMS	Upschulte, Schelling, et al., 1984	gas phase; From thermochemical cycle; M

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
8.4	296.	HPMS	Upschulte, Schelling, et al., 1984	gas phase; From thermochemical cycle; M

(O₂S^- • Sulfur dioxide ) + = (O₂S^- • 2)

By formula: (O₂S^- • O₂S) + O₂S = (O₂S^- • 2O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	8.10 ± 0.30	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B
Δ_rH°	8.3	kcal/mol	HPMS	Keesee, Lee, et al., 1980	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	16.0	cal/mol*K	HPMS	Keesee, Lee, et al., 1980	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	3.90 ± 0.20	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B

( • • Sulfur dioxide ) + = ( • 2 • )

By formula: (Cl^- • H₂O • O₂S) + H₂O = (Cl^- • 2H₂O • O₂S)

Bond type: Hydrogen bond (negative ion to hydride)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	9.30	kcal/mol	TDAs	Upschulte, Schelling, et al., 1984	gas phase; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	19.7	cal/mol*K	HPMS	Upschulte, Schelling, et al., 1984	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	3.40	kcal/mol	TDAs	Upschulte, Schelling, et al., 1984	gas phase; B

( • 2 Sulfur dioxide ) + = ( • • 2)

By formula: (Cl^- • 2O₂S) + H₂O = (Cl^- • H₂O • 2O₂S)

Bond type: Hydrogen bond (negative ion to hydride)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	9.90	kcal/mol	TDAs	Upschulte, Schelling, et al., 1984	gas phase; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	22.7	cal/mol*K	HPMS	Upschulte, Schelling, et al., 1984	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	3.10	kcal/mol	TDAs	Upschulte, Schelling, et al., 1984	gas phase; B

( • 2 Sulfur dioxide ) + = ( • 3)

By formula: (NO₂^- • 2O₂S) + O₂S = (NO₂^- • 3O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	6.60 ± 0.20	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	13.4	cal/mol*K	HPMS	Keesee, Lee, et al., 1980	gas phase; Entropy change is questionable; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	2.60 ± 0.80	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B

( • Sulfur dioxide ) + = ( • • )

By formula: (Cl^- • O₂S) + HCl = (Cl^- • HCl • O₂S)

Bond type: Hydrogen bond (negative ion to hydride)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	13.9	kcal/mol	PHPMS	Caldwell and Kebarle, 1985	gas phase; From thermochemical cycle; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	19.2	cal/mol*K	PHPMS	Caldwell and Kebarle, 1985	gas phase; From thermochemical cycle; M

( • ) + Sulfur dioxide = ( • • )

By formula: (Cl^- • H₂O) + O₂S = (Cl^- • O₂S • H₂O)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	17.4	kcal/mol	HPMS	Upschulte, Schelling, et al., 1984	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	20.2	cal/mol*K	HPMS	Upschulte, Schelling, et al., 1984	gas phase; M

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
11.5	296.	HPMS	Fehsenfeld and Ferguson, 1974	gas phase; switching reaction(Cl- H2O)H2O; M

HO₂S⁺ + Sulfur dioxide = (HO₂S⁺ • )

By formula: HO₂S⁺ + O₂S = (HO₂S⁺ • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	21.3	kcal/mol	PHPMS	Szulejko and McMahon, 1992	gas phase; M
Δ_rH°	23.2	kcal/mol	PHPMS	McMahon and Kebarle, 1986	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	25.7	cal/mol*K	PHPMS	Szulejko and McMahon, 1992	gas phase; M
Δ_rS°	27.4	cal/mol*K	PHPMS	McMahon and Kebarle, 1986	gas phase; M

( • 2 Sulfur dioxide ) + = ( • 3)

By formula: (Cl^- • 2O₂S) + O₂S = (Cl^- • 3O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	10.00 ± 0.10	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	23.1	cal/mol*K	HPMS	Keesee, Lee, et al., 1980	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	3.10 ± 0.30	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B

( • 2 Sulfur dioxide ) + = ( • 3)

By formula: (I^- • 2O₂S) + O₂S = (I^- • 3O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	9.20 ± 0.20	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	24.7	cal/mol*K	HPMS	Keesee, Lee, et al., 1980	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	1.80 ± 0.60	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B

( • Sulfur dioxide ) + = ( • 2)

By formula: (I^- • O₂S) + O₂S = (I^- • 2O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	10.10 ± 0.10	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	21.6	cal/mol*K	HPMS	Keesee, Lee, et al., 1980	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	3.60 ± 0.30	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B

( • 3 Sulfur dioxide ) + = ( • 4)

By formula: (Cl^- • 3O₂S) + O₂S = (Cl^- • 4O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	8.60 ± 0.20	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	23.2	cal/mol*K	HPMS	Keesee, Lee, et al., 1980	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	1.6 ± 1.0	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B

( • Sulfur dioxide ) + = ( • • )

By formula: (I^- • O₂S) + H₂O = (I^- • H₂O • O₂S)

Bond type: Hydrogen bond (negative ion to hydride)

Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	3.50 ± 0.10	kcal/mol	TDAs	Banic and Iribarne, 1985	gas phase; B

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
3.5	300.	HPMS	Banic and Iribarne, 1985	gas phase; electric fields; M

HO^- + Sulfur dioxide = (HO^- • )

By formula: HO^- + O₂S = (HO^- • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	61.9 ± 2.8	kcal/mol	CIDT	Squires, 1992	gas phase; Dissociative protonation between HCl, MeCHClCO2H; B
Δ_rH°	>50.9 ± 3.0	kcal/mol	IMRB	Hierl and Paulson, 1984	gas phase; CO₂..HO^- + SO₂ ->. data revised per 92SQU; B

+ Sulfur dioxide = ( • )

By formula: Br^- + O₂S = (Br^- • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	19.3 ± 2.0	kcal/mol	TDAs	Caldwell and Kebarle, 1985	gas phase; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	22.0	cal/mol*K	PHPMS	Caldwell and Kebarle, 1985	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	12.7 ± 2.6	kcal/mol	TDAs	Caldwell and Kebarle, 1985	gas phase; B

CN^- + Sulfur dioxide = (CN^- • )

By formula: CN^- + O₂S = (CN^- • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	21.70 ± 0.80	kcal/mol	TDAs	Larson, Szulejko, et al., 1988	gas phase; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	28.	cal/mol*K	PHPMS	Larson, Szulejko, et al., 1988	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	13.40 ± 0.20	kcal/mol	TDAs	Larson, Szulejko, et al., 1988	gas phase; B

+ Sulfur dioxide = ( • )

By formula: Cs⁺ + O₂S = (Cs⁺ • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	10.8	kcal/mol	DT	McKnight and Sawina, 1972	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	18.9	cal/mol*K	DT	McKnight and Sawina, 1972	gas phase; M

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
5.2	300.	HPMS	Banic and Iribarne, 1985	gas phase; electric fields; M

( • Sulfur dioxide ) + = ( • • )

By formula: (NO₂^- • O₂S) + C₂H₅NO₃ = (NO₂^- • C₂H₅NO₃ • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	7.4	kcal/mol	HPMS	Wlodek, Luczynski, et al., 1983	gas phase; Entropy change is questionable; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	10.4	cal/mol*K	HPMS	Wlodek, Luczynski, et al., 1983	gas phase; Entropy change is questionable; M

( • 2 • Sulfur dioxide ) + = ( • 3 • )

By formula: (H₄N⁺ • 2H₂O • O₂S) + H₂O = (H₄N⁺ • 3H₂O • O₂S)

Bond type: Hydrogen bond (positive ion to hydride)

Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	5.2	kcal/mol	HPMS	Banic and Iribarne, 1985	gas phase; From thermochemical cycle,switching reaction, electric fields; M

( • Sulfur dioxide ) + = ( • 2)

By formula: (NO₃^- • O₂S) + O₂S = (NO₃^- • 2O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	8.8	kcal/mol	HPMS	Wlodek, Luczynski, et al., 1983	gas phase; Entropy change is questionable; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	14.1	cal/mol*K	HPMS	Wlodek, Luczynski, et al., 1983	gas phase; Entropy change is questionable; M

( • • Sulfur dioxide ) + = ( • 2 • )

By formula: (H₄N⁺ • H₂O • O₂S) + H₂O = (H₄N⁺ • 2H₂O • O₂S)

Bond type: Hydrogen bond (positive ion to hydride)

Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	7.4	kcal/mol	HPMS	Banic and Iribarne, 1985	gas phase; From thermochemical cycle,switching reaction, electric fields; M

(O₂S^- • 2 • 3 Sulfur dioxide ) + = (O₂S^- • 3 • 3)

By formula: (O₂S^- • 2H₂O • 3O₂S) + H₂O = (O₂S^- • 3H₂O • 3O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	6.60 ± 0.30	kcal/mol	TDAs	Vacher, Leduc, et al., 1994	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	3.00 ± 0.20	kcal/mol	TDAs	Vacher, Leduc, et al., 1994	gas phase; B

(O₂S^- • 2 • 4 Sulfur dioxide ) + = (O₂S^- • 3 • 4)

By formula: (O₂S^- • 2H₂O • 4O₂S) + H₂O = (O₂S^- • 3H₂O • 4O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	7.10 ± 0.70	kcal/mol	TDAs	Vacher, Leduc, et al., 1994	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	2.60 ± 0.20	kcal/mol	TDAs	Vacher, Leduc, et al., 1994	gas phase; B

(O₂S^- • 5 Sulfur dioxide • 2) + = (O₂S^- • 6 • 2)

By formula: (O₂S^- • 5O₂S • 2H₂O) + O₂S = (O₂S^- • 6O₂S • 2H₂O)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	3.80 ± 0.90	kcal/mol	TDAs	Vacher, Leduc, et al., 1994	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	1.10 ± 0.20	kcal/mol	TDAs	Vacher, Leduc, et al., 1994	gas phase; B

(O₂S^- • 6 Sulfur dioxide • 2) + = (O₂S^- • 7 • 2)

By formula: (O₂S^- • 6O₂S • 2H₂O) + O₂S = (O₂S^- • 7O₂S • 2H₂O)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	3.70 ± 0.70	kcal/mol	TDAs	Vacher, Leduc, et al., 1994	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	0.60 ± 0.20	kcal/mol	TDAs	Vacher, Leduc, et al., 1994	gas phase; B

(O₂S^- • • 3 Sulfur dioxide ) + = (O₂S^- • 2 • 3)

By formula: (O₂S^- • H₂O • 3O₂S) + H₂O = (O₂S^- • 2H₂O • 3O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	7.10 ± 0.40	kcal/mol	TDAs	Vacher, Leduc, et al., 1994	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	3.80 ± 0.20	kcal/mol	TDAs	Vacher, Leduc, et al., 1994	gas phase; B

(O₂S^- • • 4 Sulfur dioxide ) + = (O₂S^- • 2 • 4)

By formula: (O₂S^- • H₂O • 4O₂S) + H₂O = (O₂S^- • 2H₂O • 4O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	7.10 ± 0.70	kcal/mol	TDAs	Vacher, Leduc, et al., 1994	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	3.00 ± 0.20	kcal/mol	TDAs	Vacher, Leduc, et al., 1994	gas phase; B

( • 4) + Sulfur dioxide = ( • • 4)

By formula: (H₃O⁺ • 4H₂O) + O₂S = (H₃O⁺ • O₂S • 4H₂O)

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
2.6	300.	HPMS	Banic and Iribarne, 1985	gas phase; electric fields; M
2.6	300.	HPMS	Banic and Iribarne, 1985	gas phase; electric fields; M

(O₂S^- • 6 Sulfur dioxide • ) + = (O₂S^- • 7 • )

By formula: (O₂S^- • 6O₂S • H₂O) + O₂S = (O₂S^- • 7O₂S • H₂O)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	3.20 ± 0.60	kcal/mol	TDAs	Vacher, Leduc, et al., 1994	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	0.70 ± 0.20	kcal/mol	TDAs	Vacher, Leduc, et al., 1994	gas phase; B

( • Sulfur dioxide ) + = ( • • )

By formula: (NO₃^- • O₂S) + H₂O = (NO₃^- • H₂O • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	4.30 ± 0.10	kcal/mol	TDAs	Banic and Iribarne, 1985	gas phase; B

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
4.3	299.	HPMS	Banic and Iribarne, 1985	gas phase; electric fields; M

( • ) + Sulfur dioxide = ( • • )

By formula: (I^- • H₂O) + O₂S = (I^- • O₂S • H₂O)

Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	9.00 ± 0.10	kcal/mol	TDAs	Banic and Iribarne, 1985	gas phase; B

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
7.1	300.	HPMS	Banic and Iribarne, 1985	gas phase; electric fields; M

(O₂S^- • 2 Sulfur dioxide • ) + = (O₂S^- • 3 • )

By formula: (O₂S^- • 2O₂S • O₂) + O₂S = (O₂S^- • 3O₂S • O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	3.60 ± 0.40	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	1.5 ± 3.0	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B

(O₂S^- • Sulfur dioxide • ) + = (O₂S^- • 2 • )

By formula: (O₂S^- • O₂S • O₂) + O₂S = (O₂S^- • 2O₂S • O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	4.60 ± 0.40	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	2.5 ± 2.0	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B

(O₃S^- • Sulfur dioxide • ) + = (O₃S^- • 2 • )

By formula: (O₃S^- • O₂S • O₂) + O₂S = (O₃S^- • 2O₂S • O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	5.70 ± 0.60	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	3.6 ± 2.1	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B

+ Sulfur dioxide = ( • )

By formula: CH₃⁺ + O₂S = (CH₃⁺ • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	60.6	kcal/mol	PHPMS	McMahon, Heinis, et al., 1988	gas phase; switching reaction(CH3+)N2, Entropy change calculated or estimated, uses MCA(N2) = 48.3 kcal/mol; Foster, Williamson, et al., 1974; M

Gas phase ion energetics data

Go To: Top, Gas phase thermochemistry data, Reaction thermochemistry data, Ion clustering data, Gas Chromatography, References, Notes

Data evaluated as indicated in comments:
HL - Edward P. Hunter and Sharon G. Lias
L - Sharon G. Lias

Data compiled as indicated in comments:
MM - Michael M. Meot-Ner (Mautner)
LL - Sharon G. Lias and Joel F. Liebman
LBLHLM - Sharon G. Lias, John E. Bartmess, Joel F. Liebman, John L. Holmes, Rhoda D. Levin, and W. Gary Mallard
LLK - Sharon G. Lias, Rhoda D. Levin, and Sherif A. Kafafi
RDSH - Henry M. Rosenstock, Keith Draxl, Bruce W. Steiner, and John T. Herron
B - John E. Bartmess

View reactions leading to O₂S⁺ (ion structure unspecified)

Quantity	Value	Units	Method	Reference	Comment
IE (evaluated)	12.349 ± 0.001	eV	N/A	N/A	L
Quantity	Value	Units	Method	Reference	Comment
Proton affinity (review)	160.7	kcal/mol	N/A	Hunter and Lias, 1998	HL
Quantity	Value	Units	Method	Reference	Comment
Gas basicity	153.8	kcal/mol	N/A	Hunter and Lias, 1998	HL

Electron affinity determinations

EA (eV)	Method	Reference	Comment
1.1070 ± 0.0080	LPES	Nimlos and Ellison, 1986	B
1.097 ± 0.036	LPES	Celotta, Bennett, et al., 1974	B
1.10 ± 0.10	TDEq	Chowdhury, Heinis, et al., 1986	ΔGea(423 K) = -26.1 kcal/mol; ΔSea (estimated) = +2.0 eu. Original: Caldwell and Kebarle, 19842. Not direct measurement, but anchor for extensiveEA equilibrium scale. See text.; B
1.10 ± 0.20	IMRB	Grabowski, VanDoren, et al., 1984	B
1.04998	Endo	Refaey and Franklin, 1976	B
1.00 ± 0.10	Endo	Hughes, Lifschitz, et al., 1973	B
1.00 ± 0.050	PD	Feldman, 1970	B
1.06 ± 0.10	IMRB	Kraus, Muller-Duysing, et al., 1961	Between NH₂^-, C^-; B
1.14 ± 0.15	NBIE	Rothe, Tang, et al., 1975	B

Gas basicity at 298K

Gas basicity (review) (kcal/mol)	Reference	Comment
<149.	Milligan, Fairley, et al., 1998	Irreversible PT from SO2H+ to C2N2 shows GB(SO2) < GB(C2N2), and using GB(C2N2) for reference from this paper; MM
<145.	Milligan, Fairley, et al., 1998	Irreversible PT from SO2H+ to C2H2 shows GB(SO2) < (GB(C2H2) + 4.5 kcal/mol); MM

Ionization energy determinations

IE (eV)	Method	Reference	Comment
12.5 ± 0.1	EI	Snow and Thomas, 1990	LL
12.3494 ± 0.0002	PE	Wang, Lee, et al., 1987	LBLHLM
12.5 ± 0.3	EI	Orient and Srivastava, 1984	LBLHLM
12.4 ± 0.2	EI	Smith and Stevenson, 1981	LLK
12.3	PE	Lloyd and Roberts, 1973	LLK
12.31	PE	Bock, Solouki, et al., 1973	LLK
12.30 ± 0.01	PE	Eland and Danby, 1968	RDSH
12.32 ± 0.01	PI	Dibeler and Liston, 1968	RDSH
12.34	S	Golomb, Watanabe, et al., 1962	RDSH
12.34 ± 0.02	PI	Watanabe, 1957	RDSH
12.50	PE	Kimura, Katsumata, et al., 1981	Vertical value; LLK
12.54	PE	Kroner, Strack, et al., 1973	Vertical value; LLK
12.50	PE	Chadwick, Frost, et al., 1973	Vertical value; LLK

Appearance energy determinations

Ion	AE (eV)	Other Products	Method	Reference	Comment
O⁺	23.5 ± 0.5	SO	EI	Orient and Srivastava, 1984	LBLHLM
O⁺	20.6	SO	EI	Reese, Dibeter, et al., 1958	RDSH
OS⁺	16.5 ± 0.5	O	EI	Orient and Srivastava, 1984	LBLHLM
OS⁺	16.2 ± 0.2	O	EI	Smith and Stevenson, 1981	LLK
OS⁺	15.930 ± 0.005	O	PE	Weiss, Hsieh, et al., 1979	LLK
SO⁺	15.81 ± 0.02	O	PI	Dibeler and Liston, 1968	RDSH
O₂⁺	17.5 ± 0.3	S	EI	Reese, Dibeter, et al., 1958	RDSH
S⁺	16.5 ± 0.5	O₂/2O	EI	Orient and Srivastava, 1984	LBLHLM
S⁺	22.	2O	EI	Smith and Stevenson, 1981	LLK
S⁺	16.334	O₂/2O	PE	Weiss, Hsieh, et al., 1979	LLK
S⁺	17.5 ± 0.3	O₂	EI	Reese, Dibeter, et al., 1958	RDSH

Ion clustering data

Go To: Top, Gas phase thermochemistry data, Reaction thermochemistry data, Gas phase ion energetics data, Gas Chromatography, References, Notes

Data compiled as indicated in comments:
M - Michael M. Meot-Ner (Mautner) and Sharon G. Lias
B - John E. Bartmess

Note: Please consider using the reaction search for this species. This page allows searching of all reactions involving this species. Searches may be limited to ion clustering reactions. A general reaction search form is also available.

Clustering reactions

( • ) + Sulfur dioxide = ( • • )

By formula: (Br^- • HBr) + O₂S = (Br^- • O₂S • HBr)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	10.9	kcal/mol	PHPMS	Caldwell and Kebarle, 1985	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	18.9	cal/mol*K	PHPMS	Caldwell and Kebarle, 1985	gas phase; M

( • ) + Sulfur dioxide = ( • • )

By formula: (Br^- • HCl) + O₂S = (Br^- • O₂S • HCl)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	12.1	kcal/mol	PHPMS	Caldwell and Kebarle, 1985	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	18.6	cal/mol*K	PHPMS	Caldwell and Kebarle, 1985	gas phase; M

+ Sulfur dioxide = ( • )

By formula: Br^- + O₂S = (Br^- • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	19.3 ± 2.0	kcal/mol	TDAs	Caldwell and Kebarle, 1985	gas phase; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	22.0	cal/mol*K	PHPMS	Caldwell and Kebarle, 1985	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	12.7 ± 2.6	kcal/mol	TDAs	Caldwell and Kebarle, 1985	gas phase; B

( • Sulfur dioxide ) + = ( • 2)

By formula: (Br^- • O₂S) + O₂S = (Br^- • 2O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	11.2	kcal/mol	PHPMS	Caldwell and Kebarle, 1985	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	18.7	cal/mol*K	PHPMS	Caldwell and Kebarle, 1985	gas phase; M

( • 2 Sulfur dioxide ) + = ( • 3)

By formula: (Br^- • 2O₂S) + O₂S = (Br^- • 3O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	8.5	kcal/mol	PHPMS	Caldwell and Kebarle, 1985	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	13.8	cal/mol*K	PHPMS	Caldwell and Kebarle, 1985	gas phase; M

+ Sulfur dioxide = ( • )

By formula: CH₃⁺ + O₂S = (CH₃⁺ • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	60.6	kcal/mol	PHPMS	McMahon, Heinis, et al., 1988	gas phase; switching reaction(CH3+)N2, Entropy change calculated or estimated, uses MCA(N2) = 48.3 kcal/mol; Foster, Williamson, et al., 1974; M

CN^- + Sulfur dioxide = (CN^- • )

By formula: CN^- + O₂S = (CN^- • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	21.70 ± 0.80	kcal/mol	TDAs	Larson, Szulejko, et al., 1988	gas phase; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	28.	cal/mol*K	PHPMS	Larson, Szulejko, et al., 1988	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	13.40 ± 0.20	kcal/mol	TDAs	Larson, Szulejko, et al., 1988	gas phase; B

CO₃^- + Sulfur dioxide = (CO₃^- • )

By formula: CO₃^- + O₂S = (CO₃^- • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	14.	kcal/mol	HPMS	Keesee, Lee, et al., 1980	gas phase; switching reaction(O-)CO2, Entropy change calculated or estimated; Fehsenfeld and Ferguson, 1974; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	20.	cal/mol*K	N/A	Keesee, Lee, et al., 1980	gas phase; switching reaction(O-)CO2, Entropy change calculated or estimated; Fehsenfeld and Ferguson, 1974; M

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
8.0	296.	HPMS	Keesee, Lee, et al., 1980	gas phase; switching reaction(O-)CO2, Entropy change calculated or estimated; Fehsenfeld and Ferguson, 1974; M

C₄H₆⁺ + Sulfur dioxide = (C₄H₆⁺ • )

By formula: C₄H₆⁺ + O₂S = (C₄H₆⁺ • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	3.7	kcal/mol	PI	Grover, Walters, et al., 1985	gas phase; M

C₄H₈⁺ + Sulfur dioxide = (C₄H₈⁺ • )

By formula: C₄H₈⁺ + O₂S = (C₄H₈⁺ • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.4	kcal/mol	PI	Grover, Walters, et al., 1985	gas phase; M

C₄H₈⁺ + Sulfur dioxide = (C₄H₈⁺ • )

By formula: C₄H₈⁺ + O₂S = (C₄H₈⁺ • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.4	kcal/mol	PI	Grover, Walters, et al., 1985	gas phase; M

( • ) + Sulfur dioxide = ( • • )

By formula: (Cl^- • HCl) + O₂S = (Cl^- • O₂S • HCl)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	12.3	kcal/mol	PHPMS	Caldwell and Kebarle, 1985	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	18.5	cal/mol*K	PHPMS	Caldwell and Kebarle, 1985	gas phase; M

( • ) + Sulfur dioxide = ( • • )

By formula: (Cl^- • H₂O) + O₂S = (Cl^- • O₂S • H₂O)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	17.4	kcal/mol	HPMS	Upschulte, Schelling, et al., 1984	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	20.2	cal/mol*K	HPMS	Upschulte, Schelling, et al., 1984	gas phase; M

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
11.5	296.	HPMS	Fehsenfeld and Ferguson, 1974	gas phase; switching reaction(Cl- H2O)H2O; M

( • 2) + Sulfur dioxide = ( • • 2)

By formula: (Cl^- • 2H₂O) + O₂S = (Cl^- • O₂S • 2H₂O)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	14.1	kcal/mol	HPMS	Upschulte, Schelling, et al., 1984	gas phase; From thermochemical cycle; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	19.4	cal/mol*K	HPMS	Upschulte, Schelling, et al., 1984	gas phase; From thermochemical cycle; M

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
8.4	296.	HPMS	Upschulte, Schelling, et al., 1984	gas phase; From thermochemical cycle; M

+ Sulfur dioxide = ( • )

By formula: Cl^- + O₂S = (Cl^- • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	22.2 ± 2.0	kcal/mol	TDAs	Caldwell and Kebarle, 1985	gas phase; B,M
Δ_rH°	20.9 ± 2.0	kcal/mol	IMRE	Larson and McMahon, 1985	gas phase; B
Δ_rH°	22.2 ± 2.2	kcal/mol	TDEq	Bohringer, Fahey, et al., 1984	gas phase; Relative to HOH..Cl^- in Keesee, Lee, et al., 1980; B,M
Δ_rH°	21.80 ± 0.20	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B,M
Δ_rH°	20.9	kcal/mol	ICR	Larson and McMahon, 1984	gas phase; switching reaction(Cl-)t-C4H9OH, Entropy change calculated or estimated; French, Ikuta, et al., 1982; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	21.6	cal/mol*K	PHPMS	Caldwell and Kebarle, 1985	gas phase; M
Δ_rS°	24.1	cal/mol*K	N/A	Bohringer, Fahey, et al., 1984	gas phase; switching reaction(Cl-)H2O), Entropy change calculated or estimated; Keesee and Castleman, 1980; M
Δ_rS°	20.8	cal/mol*K	N/A	Larson and McMahon, 1984	gas phase; switching reaction(Cl-)t-C4H9OH, Entropy change calculated or estimated; French, Ikuta, et al., 1982; M
Δ_rS°	23.2	cal/mol*K	HPMS	Keesee, Lee, et al., 1980	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	15.7 ± 2.0	kcal/mol	TDAs	Caldwell and Kebarle, 1985	gas phase; B
Δ_rG°	14.7 ± 2.0	kcal/mol	IMRE	Larson and McMahon, 1985	gas phase; B
Δ_rG°	15.0 ± 1.6	kcal/mol	TDEq	Bohringer, Fahey, et al., 1984	gas phase; Relative to HOH..Cl^- in Keesee, Lee, et al., 1980; B,M
Δ_rG°	14.80 ± 0.30	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B
Δ_rG°	14.7	kcal/mol	ICR	Larson and McMahon, 1984	gas phase; switching reaction(Cl-)t-C4H9OH, Entropy change calculated or estimated; French, Ikuta, et al., 1982; M

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
14.2	296.	FA	Fehsenfeld and Ferguson, 1974	gas phase; switching reaction(Cl-)H2O; M

( • Sulfur dioxide • ) + = ( • 2 • )

By formula: (Cl^- • O₂S • H₂O) + O₂S = (Cl^- • 2O₂S • H₂O)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	11.8	kcal/mol	HPMS	Upschulte, Schelling, et al., 1984	gas phase; From thermochemical cycle; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	26.0	cal/mol*K	HPMS	Upschulte, Schelling, et al., 1984	gas phase; From thermochemical cycle; M

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
4.1	296.	HPMS	Upschulte, Schelling, et al., 1984	gas phase; From thermochemical cycle; M

( • Sulfur dioxide ) + = ( • 2)

By formula: (Cl^- • O₂S) + O₂S = (Cl^- • 2O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	12.3 ± 1.0	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B,M
Δ_rH°	12.3	kcal/mol	PHPMS	Caldwell and Kebarle, 1985	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	20.2	cal/mol*K	PHPMS	Caldwell and Kebarle, 1985	gas phase; M
Δ_rS°	22.7	cal/mol*K	HPMS	Keesee, Lee, et al., 1980	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	5.5 ± 2.2	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B

( • 2 Sulfur dioxide ) + = ( • 3)

By formula: (Cl^- • 2O₂S) + O₂S = (Cl^- • 3O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	10.00 ± 0.10	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	23.1	cal/mol*K	HPMS	Keesee, Lee, et al., 1980	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	3.10 ± 0.30	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B

( • 3 Sulfur dioxide ) + = ( • 4)

By formula: (Cl^- • 3O₂S) + O₂S = (Cl^- • 4O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	8.60 ± 0.20	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	23.2	cal/mol*K	HPMS	Keesee, Lee, et al., 1980	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	1.6 ± 1.0	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B

ClO₄^- + Sulfur dioxide = (ClO₄^- • )

By formula: ClO₄^- + O₂S = (ClO₄^- • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	5.70 ± 0.10	kcal/mol	TDAs	Banic and Iribarne, 1985	gas phase; B

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
5.7	290.	HPMS	Banic and Iribarne, 1985	gas phase; electric fields; M

( • ) + Sulfur dioxide = ( • • )

By formula: (Cs⁺ • H₂O) + O₂S = (Cs⁺ • O₂S • H₂O)

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
4.3	300.	HPMS	Banic and Iribarne, 1985	gas phase; electric fields; M

( • 2) + Sulfur dioxide = ( • • 2)

By formula: (Cs⁺ • 2H₂O) + O₂S = (Cs⁺ • O₂S • 2H₂O)

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
3.5	300.	HPMS	Banic and Iribarne, 1985	gas phase; electric fields; M

+ Sulfur dioxide = ( • )

By formula: Cs⁺ + O₂S = (Cs⁺ • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	10.8	kcal/mol	DT	McKnight and Sawina, 1972	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	18.9	cal/mol*K	DT	McKnight and Sawina, 1972	gas phase; M

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
5.2	300.	HPMS	Banic and Iribarne, 1985	gas phase; electric fields; M

+ Sulfur dioxide = ( • )

By formula: F^- + O₂S = (F^- • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	53.8 ± 2.2	kcal/mol	CIDT	Lobring, Check, et al., 2003	gas phase; B
Δ_rH°	53.0 ± 2.5	kcal/mol	CIDT	Squires, 1992	gas phase; B
Δ_rH°	43.8	kcal/mol	ICR	Larson and McMahon, 1985	gas phase; switching reaction(F-)H2O, Entropy change calculated or estimated; Arshadi, Yamdagni, et al., 1970; M
Δ_rH°	43.8 ± 2.0	kcal/mol	IMRE	Larson and McMahon, 1983	gas phase; These relative affinities are ca. 10 kcal/mol weaker than threshold values (see Wenthold and Squires, 1995) for donors greater than ca. 27 kcal/mol in free energy. This discrepancy has not yet been resolved, though the stronger value appears preferable.; B,M
Δ_rH°	59.	kcal/mol	SAMS	Robbiani and Franklin, 1979	gas phase; Cl- + CO2ClF --> SO2F- + Cl2, Δ_rH>; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	24.	cal/mol*K	N/A	Larson and McMahon, 1985	gas phase; switching reaction(F-)H2O, Entropy change calculated or estimated; Arshadi, Yamdagni, et al., 1970; M
Δ_rS°	23.0	cal/mol*K	N/A	Larson and McMahon, 1983	gas phase; switching reaction(F-)H2O, Entropy change calculated or estimated; Arshadi, Yamdagni, et al., 1970; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	36.6	kcal/mol	ICR	Larson and McMahon, 1985	gas phase; switching reaction(F-)H2O, Entropy change calculated or estimated; Arshadi, Yamdagni, et al., 1970; M
Δ_rG°	36.9 ± 2.0	kcal/mol	IMRE	Larson and McMahon, 1983	gas phase; These relative affinities are ca. 10 kcal/mol weaker than threshold values (see Wenthold and Squires, 1995) for donors greater than ca. 27 kcal/mol in free energy. This discrepancy has not yet been resolved, though the stronger value appears preferable.; B,M

+ Sulfur dioxide = ( • )

By formula: H^- + O₂S = (H^- • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	63. ± 16.	kcal/mol	IMRB	Sheldon, Currie, et al., 1985	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	57. ± 16.	kcal/mol	IMRB	Sheldon, Currie, et al., 1985	gas phase; B

HO^- + Sulfur dioxide = (HO^- • )

By formula: HO^- + O₂S = (HO^- • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	61.9 ± 2.8	kcal/mol	CIDT	Squires, 1992	gas phase; Dissociative protonation between HCl, MeCHClCO2H; B
Δ_rH°	>50.9 ± 3.0	kcal/mol	IMRB	Hierl and Paulson, 1984	gas phase; CO₂..HO^- + SO₂ ->. data revised per 92SQU; B

HO₂S⁺ + Sulfur dioxide = (HO₂S⁺ • )

By formula: HO₂S⁺ + O₂S = (HO₂S⁺ • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	21.3	kcal/mol	PHPMS	Szulejko and McMahon, 1992	gas phase; M
Δ_rH°	23.2	kcal/mol	PHPMS	McMahon and Kebarle, 1986	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	25.7	cal/mol*K	PHPMS	Szulejko and McMahon, 1992	gas phase; M
Δ_rS°	27.4	cal/mol*K	PHPMS	McMahon and Kebarle, 1986	gas phase; M

HO₄S^- + Sulfur dioxide = (HO₄S^- • )

By formula: HO₄S^- + O₂S = (HO₄S^- • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	13.7	kcal/mol	HPMS	Keesee and Castleman, 1986	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	26.1	cal/mol*K	HPMS	Keesee and Castleman, 1986	gas phase; M

( • 3) + Sulfur dioxide = ( • • 3)

By formula: (H₃O⁺ • 3H₂O) + O₂S = (H₃O⁺ • O₂S • 3H₂O)

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
4.2	300.	HPMS	Banic and Iribarne, 1985	gas phase; electric fields; M

( • 4) + Sulfur dioxide = ( • • 4)

By formula: (H₃O⁺ • 4H₂O) + O₂S = (H₃O⁺ • O₂S • 4H₂O)

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
2.6	300.	HPMS	Banic and Iribarne, 1985	gas phase; electric fields; M
2.6	300.	HPMS	Banic and Iribarne, 1985	gas phase; electric fields; M

+ Sulfur dioxide = ( • )

By formula: H₃O⁺ + O₂S = (H₃O⁺ • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	22.0	kcal/mol	PHPMS	Szulejko and McMahon, 1992	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	22.7	cal/mol*K	PHPMS	Szulejko and McMahon, 1992	gas phase; M

( • ) + Sulfur dioxide = ( • • )

By formula: (H₄N⁺ • H₂O) + O₂S = (H₄N⁺ • O₂S • H₂O)

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
6.4	300.	HPMS	Banic and Iribarne, 1985	gas phase; electric fields; M

( • 2) + Sulfur dioxide = ( • • 2)

By formula: (H₄N⁺ • 2H₂O) + O₂S = (H₄N⁺ • O₂S • 2H₂O)

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
5.0	300.	HPMS	Banic and Iribarne, 1985	gas phase; electric fields; M

( • 3) + Sulfur dioxide = ( • • 3)

By formula: (H₄N⁺ • 3H₂O) + O₂S = (H₄N⁺ • O₂S • 3H₂O)

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
3.6	300.	HPMS	Banic and Iribarne, 1985	gas phase; electric fields; M

( • ) + Sulfur dioxide = ( • • )

By formula: (I^- • H₂O) + O₂S = (I^- • O₂S • H₂O)

Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	9.00 ± 0.10	kcal/mol	TDAs	Banic and Iribarne, 1985	gas phase; B

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
7.1	300.	HPMS	Banic and Iribarne, 1985	gas phase; electric fields; M

+ Sulfur dioxide = ( • )

By formula: I^- + O₂S = (I^- • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	14.3 ± 2.0	kcal/mol	TDAs	Caldwell and Kebarle, 1985	gas phase; B,M
Δ_rH°	12.90 ± 0.10	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	17.6	cal/mol*K	PHPMS	Caldwell and Kebarle, 1985	gas phase; M
Δ_rS°	20.2	cal/mol*K	HPMS	Keesee, Lee, et al., 1980	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	9.0 ± 2.6	kcal/mol	TDAs	Caldwell and Kebarle, 1985	gas phase; B
Δ_rG°	1.70 ± 0.10	kcal/mol	TDAs	Banic and Iribarne, 1985	gas phase; B
Δ_rG°	6.80 ± 0.20	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
9.0	301.	HPMS	Banic and Iribarne, 1985	gas phase; electric fields; M

( • Sulfur dioxide • ) + = ( • 2 • )

By formula: (I^- • O₂S • H₂O) + O₂S = (I^- • 2O₂S • H₂O)

Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	7.10 ± 0.10	kcal/mol	TDAs	Banic and Iribarne, 1985	gas phase; B

( • Sulfur dioxide ) + = ( • 2)

By formula: (I^- • O₂S) + O₂S = (I^- • 2O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	10.10 ± 0.10	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	21.6	cal/mol*K	HPMS	Keesee, Lee, et al., 1980	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	3.60 ± 0.30	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B

( • 2 Sulfur dioxide ) + = ( • 3)

By formula: (I^- • 2O₂S) + O₂S = (I^- • 3O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	9.20 ± 0.20	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	24.7	cal/mol*K	HPMS	Keesee, Lee, et al., 1980	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	1.80 ± 0.60	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B

+ Sulfur dioxide = ( • )

By formula: NO^- + O₂S = (NO^- • O₂S)

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
7.8	296.	SAMS	Vanderhoff and Heimerl, 1977	gas phase; switching reaction(NO+)NO; Puckett and Teague, 1971; M

+ Sulfur dioxide = ( • )

By formula: NO₂^- + O₂S = (NO₂^- • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	25.90 ± 0.20	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B,M
Δ_rH°	24.3 ± 1.0	kcal/mol	TDEq	Bohringer, Fahey, et al., 1984	gas phase; Relative to HOH..NO₂^-, Keesee, Lee, et al., 1980; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	36.8	cal/mol*K	HPMS	Keesee, Lee, et al., 1980	gas phase; M
Δ_rS°	31.6	cal/mol*K	N/A	Bohringer, Fahey, et al., 1984	gas phase; switching reaction(NO2-)H2O, Entropy change calculated or estimated; Lee, Keesee, et al., 1980; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	14.90 ± 0.30	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B

( • Sulfur dioxide ) + = ( • 2)

By formula: (NO₂^- • O₂S) + O₂S = (NO₂^- • 2O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	9.00 ± 0.20	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B,M
Δ_rH°	9.8	kcal/mol	HPMS	Wlodek, Luczynski, et al., 1983	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	21.5	cal/mol*K	HPMS	Wlodek, Luczynski, et al., 1983	gas phase; M
Δ_rS°	16.8	cal/mol*K	HPMS	Keesee, Lee, et al., 1980	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	4.00 ± 0.40	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B

( • 2 Sulfur dioxide ) + = ( • 3)

By formula: (NO₂^- • 2O₂S) + O₂S = (NO₂^- • 3O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	6.60 ± 0.20	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	13.4	cal/mol*K	HPMS	Keesee, Lee, et al., 1980	gas phase; Entropy change is questionable; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	2.60 ± 0.80	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B

( • ) + Sulfur dioxide = ( • • )

By formula: (NO₃^- • H₂O) + O₂S = (NO₃^- • O₂S • H₂O)

Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	7.2	kcal/mol	HPMS	Banic and Iribarne, 1985	gas phase; From thermochemical cycle,switching reaction, electric fields; M

+ Sulfur dioxide = ( • )

By formula: NO₃^- + O₂S = (NO₃^- • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	17.2 ± 2.0	kcal/mol	TDEq	Bohringer, Fahey, et al., 1984	gas phase; Relative to HOH..NO₃^-, Keesee, Lee, et al., 1980; B,M
Δ_rH°	18.2 ± 1.2	kcal/mol	TDAs	Wlodek, Luczynski, et al., 1983	gas phase; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	25.2	cal/mol*K	N/A	Bohringer, Fahey, et al., 1984	gas phase; switching reaction(NO3-)H2O, Entropy change calculated or estimated; Lee, Keesee, et al., 1980; M
Δ_rS°	31.6	cal/mol*K	HPMS	Wlodek, Luczynski, et al., 1983	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	9.6 ± 2.0	kcal/mol	TDEq	Bohringer, Fahey, et al., 1984	gas phase; Relative to HOH..NO₃^-, Keesee, Lee, et al., 1980; B,M
Δ_rG°	10.00 ± 0.10	kcal/mol	TDAs	Banic and Iribarne, 1985	gas phase; B
Δ_rG°	8.80 ± 0.90	kcal/mol	TDAs	Wlodek, Luczynski, et al., 1983	gas phase; B
Δ_rG°	10.6	kcal/mol	FA	Fehsenfeld and Ferguson, 1974	gas phase; switching reaction(NO3-)SO2, Entropy change calculated or estimated; Lee, Keesee, et al., 1980; M

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
10.0	299.	HPMS	Banic and Iribarne, 1985	gas phase; electric fields; M

( • Sulfur dioxide ) + = ( • 2)

By formula: (NO₃^- • O₂S) + O₂S = (NO₃^- • 2O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	8.8	kcal/mol	HPMS	Wlodek, Luczynski, et al., 1983	gas phase; Entropy change is questionable; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	14.1	cal/mol*K	HPMS	Wlodek, Luczynski, et al., 1983	gas phase; Entropy change is questionable; M

( • ) + Sulfur dioxide = ( • • )

By formula: (Na⁺ • H₂O) + O₂S = (Na⁺ • O₂S • H₂O)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	14.1	kcal/mol	HPMS	Upschulte, Schelling, et al., 1984	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	17.4	cal/mol*K	HPMS	Upschulte, Schelling, et al., 1984	gas phase; M

( • 3) + Sulfur dioxide = ( • • 3)

By formula: (Na⁺ • 3H₂O) + O₂S = (Na⁺ • O₂S • 3H₂O)

Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	4.8	kcal/mol	HPMS	Banic and Iribarne, 1985	gas phase; electric fields; M

+ Sulfur dioxide = ( • )

By formula: Na⁺ + O₂S = (Na⁺ • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	18.9	kcal/mol	FA	Perry, Rowe, et al., 1980	gas phase; Entropy change calculated or estimated; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	20.3	cal/mol*K	N/A	Perry, Rowe, et al., 1980	gas phase; Entropy change calculated or estimated; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	12.8	kcal/mol	FA	Perry, Rowe, et al., 1980	gas phase; Entropy change calculated or estimated; M

( • Sulfur dioxide ) + = ( • 2)

By formula: (Na⁺ • O₂S) + O₂S = (Na⁺ • 2O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	16.6	kcal/mol	HPMS	Castleman, Peterson, et al., 1983	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	25.5	cal/mol*K	HPMS	Castleman, Peterson, et al., 1983	gas phase; M

( • 2 Sulfur dioxide ) + = ( • 3)

By formula: (Na⁺ • 2O₂S) + O₂S = (Na⁺ • 3O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	14.3	kcal/mol	HPMS	Castleman, Peterson, et al., 1983	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	26.9	cal/mol*K	HPMS	Castleman, Peterson, et al., 1983	gas phase; M

( • 3 Sulfur dioxide ) + = ( • 4)

By formula: (Na⁺ • 3O₂S) + O₂S = (Na⁺ • 4O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	12.3	kcal/mol	HPMS	Castleman, Peterson, et al., 1983	gas phase; Entropy change calculated or estimated; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	27.	cal/mol*K	N/A	Castleman, Peterson, et al., 1983	gas phase; Entropy change calculated or estimated; M

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
3.2	328.	HPMS	Castleman, Peterson, et al., 1983	gas phase; Entropy change calculated or estimated; M

O^- + Sulfur dioxide = (O^- • )

By formula: O^- + O₂S = (O^- • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	60.	kcal/mol	FA	Fehsenfeld and Ferguson, 1974	gas phase; switching reaction(O-)CO2, Δ_rH>; Hiller and Vestal, 1980, Keesee and Castleman, 1986; M

(O^- • Sulfur dioxide ) + = (O^- • 2)

By formula: (O^- • O₂S) + O₂S = (O^- • 2O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	13.3	kcal/mol	HPMS	Keesee, Lee, et al., 1980	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	18.9	cal/mol*K	HPMS	Keesee, Lee, et al., 1980	gas phase; M

OS⁺ + Sulfur dioxide = (OS⁺ • )

By formula: OS⁺ + O₂S = (OS⁺ • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	13.8	kcal/mol	PI	Erickson and Ng, 1981	gas phase; M

+ Sulfur dioxide = ( • )

By formula: O₂⁺ + O₂S = (O₂⁺ • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	9.6	kcal/mol	FA	Adams and Bohme, 1970	gas phase; switching reaction(O2+)O2; Conway and Janik, 1970; M

O₂S⁺ + Sulfur dioxide = (O₂S⁺ • )

By formula: O₂S⁺ + O₂S = (O₂S⁺ • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	15.2	kcal/mol	PI	Erickson and Ng, 1981	gas phase; M

O₂S^- + Sulfur dioxide = (O₂S^- • )

By formula: O₂S^- + O₂S = (O₂S^- • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	24.00 ± 0.20	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B,M
Δ_rH°	21.3 ± 1.3	kcal/mol	TDAs	Vacher, Leduc, et al., 1994	gas phase; B
Δ_rH°	18.50	kcal/mol	N/A	Dresch, Kramer, et al., 1991	gas phase; Both dissociation and electron detachment?; B
Δ_rH°	18.30	kcal/mol	N/A	Snodgrass, Coe, et al., 1988	gas phase; Appears to be dissociation + electron detachment; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	33.8	cal/mol*K	HPMS	Keesee, Lee, et al., 1980	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	13.90 ± 0.40	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B
Δ_rG°	10.4 ± 2.2	kcal/mol	TDAs	Vacher, Leduc, et al., 1994	gas phase; B

(O₂S^- • 5 Sulfur dioxide • 2) + = (O₂S^- • 6 • 2)

By formula: (O₂S^- • 5O₂S • 2H₂O) + O₂S = (O₂S^- • 6O₂S • 2H₂O)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	3.80 ± 0.90	kcal/mol	TDAs	Vacher, Leduc, et al., 1994	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	1.10 ± 0.20	kcal/mol	TDAs	Vacher, Leduc, et al., 1994	gas phase; B

(O₂S^- • 6 Sulfur dioxide • ) + = (O₂S^- • 7 • )

By formula: (O₂S^- • 6O₂S • H₂O) + O₂S = (O₂S^- • 7O₂S • H₂O)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	3.20 ± 0.60	kcal/mol	TDAs	Vacher, Leduc, et al., 1994	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	0.70 ± 0.20	kcal/mol	TDAs	Vacher, Leduc, et al., 1994	gas phase; B

(O₂S^- • 6 Sulfur dioxide • 2) + = (O₂S^- • 7 • 2)

By formula: (O₂S^- • 6O₂S • 2H₂O) + O₂S = (O₂S^- • 7O₂S • 2H₂O)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	3.70 ± 0.70	kcal/mol	TDAs	Vacher, Leduc, et al., 1994	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	0.60 ± 0.20	kcal/mol	TDAs	Vacher, Leduc, et al., 1994	gas phase; B

(O₂S^- • Sulfur dioxide ) + = (O₂S^- • 2)

By formula: (O₂S^- • O₂S) + O₂S = (O₂S^- • 2O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	8.10 ± 0.30	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B
Δ_rH°	8.3	kcal/mol	HPMS	Keesee, Lee, et al., 1980	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	16.0	cal/mol*K	HPMS	Keesee, Lee, et al., 1980	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	3.90 ± 0.20	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B

(O₂S^- • 2 Sulfur dioxide ) + = (O₂S^- • 3)

By formula: (O₂S^- • 2O₂S) + O₂S = (O₂S^- • 3O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	6.40 ± 0.20	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	3.00 ± 0.20	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B

(O₂S^- • 3 Sulfur dioxide ) + = (O₂S^- • 4)

By formula: (O₂S^- • 3O₂S) + O₂S = (O₂S^- • 4O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	5.40 ± 0.30	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	2.20 ± 0.20	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B

(O₂S^- • 4 Sulfur dioxide ) + = (O₂S^- • 5)

By formula: (O₂S^- • 4O₂S) + O₂S = (O₂S^- • 5O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	4.20 ± 0.20	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	1.20 ± 0.20	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B

(O₂S^- • 5 Sulfur dioxide ) + = (O₂S^- • 6)

By formula: (O₂S^- • 5O₂S) + O₂S = (O₂S^- • 6O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	3.60 ± 0.30	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	0.90 ± 0.20	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B

(O₂S^- • 6 Sulfur dioxide ) + = (O₂S^- • 7)

By formula: (O₂S^- • 6O₂S) + O₂S = (O₂S^- • 7O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	3.40 ± 0.20	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	0.50 ± 0.20	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B

(O₂S^- • 7 Sulfur dioxide ) + = (O₂S^- • 8)

By formula: (O₂S^- • 7O₂S) + O₂S = (O₂S^- • 8O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	3.40 ± 0.30	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	0.3 ± 1.2	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B

(O₂S^- • 8 Sulfur dioxide ) + = (O₂S^- • 9)

By formula: (O₂S^- • 8O₂S) + O₂S = (O₂S^- • 9O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	3.00 ± 0.40	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	0.3 ± 1.5	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B

(O₂S^- • 9 Sulfur dioxide ) + = (O₂S^- • 10)

By formula: (O₂S^- • 9O₂S) + O₂S = (O₂S^- • 10O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	3.00 ± 0.60	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	0.1 ± 2.3	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B

(O₂S^- • Sulfur dioxide • ) + = (O₂S^- • 2 • )

By formula: (O₂S^- • O₂S • O₂) + O₂S = (O₂S^- • 2O₂S • O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	4.60 ± 0.40	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	2.5 ± 2.0	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B

(O₂S^- • 2 Sulfur dioxide • ) + = (O₂S^- • 3 • )

By formula: (O₂S^- • 2O₂S • O₂) + O₂S = (O₂S^- • 3O₂S • O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	3.60 ± 0.40	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	1.5 ± 3.0	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B

(O₂S^- • ) + Sulfur dioxide = (O₂S^- • • )

By formula: (O₂S^- • O₂) + O₂S = (O₂S^- • O₂S • O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	11.0 ± 1.0	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	6.2 ± 2.2	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B

O₃S^- + Sulfur dioxide = (O₃S^- • )

By formula: O₃S^- + O₂S = (O₃S^- • O₂S)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	13.30 ± 0.10	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	7.60 ± 0.20	kcal/mol	TDAs	Keesee, Lee, et al., 1980	gas phase; B

(O₃S^- • Sulfur dioxide • ) + = (O₃S^- • 2 • )

By formula: (O₃S^- • O₂S • O₂) + O₂S = (O₃S^- • 2O₂S • O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	5.70 ± 0.60	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	3.6 ± 2.1	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B

(O₃S^- • ) + Sulfur dioxide = (O₃S^- • • )

By formula: (O₃S^- • O₂) + O₂S = (O₃S^- • O₂S • O₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	6.50 ± 0.80	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	4.4 ± 2.2	kcal/mol	TDAs	Vacher, Jorda, et al., 1992	gas phase; B

O₄S^- + Sulfur dioxide = (O₄S^- • )

By formula: O₄S^- + O₂S = (O₄S^- • O₂S)

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
6.7	296.	FA	Fehsenfeld and Ferguson, 1974	gas phase; switching reaction(SO4-)H2O; M

Gas Chromatography

Go To: Top, Gas phase thermochemistry data, Reaction thermochemistry data, Gas phase ion energetics data, Ion clustering data, References, Notes

Data compiled by: NIST Mass Spectrometry Data Center, William E. Wallace, director

Van Den Dool and Kratz RI, polar column, temperature ramp

View large format table.

Column type	Active phase	I	Reference	Comment
Capillary	CP-Wax 52CB	856.	Mahadevan and Farmer, 2006	60. C @ 5. min, 4. K/min, 220. C @ 30. min; Column length: 50. m; Column diameter: 0.32 mm

Normal alkane RI, polar column, temperature ramp

View large format table.

Column type	Active phase	I	Reference	Comment
Capillary	DB-Wax	882.	Chyau and Mau, 1999	60. m/0.25 mm/0.25 μm, N2, 3. K/min; T_start: 40. C; T_end: 210. C

References

Go To: Top, Gas phase thermochemistry data, Reaction thermochemistry data, Gas phase ion energetics data, Ion clustering data, Gas Chromatography, Notes

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Notes

Go To: Top, Gas phase thermochemistry data, Reaction thermochemistry data, Gas phase ion energetics data, Ion clustering data, Gas Chromatography, References

Symbols used in this document:

AE	Appearance energy
EA	Electron affinity
IE (evaluated)	Recommended ionization energy
S°_{gas,1 bar}	Entropy of gas at standard conditions (1 bar)
T	Temperature
Δ_fH°_gas	Enthalpy of formation of gas at standard conditions
Δ_rG°	Free energy of reaction at standard conditions
Δ_rH°	Enthalpy of reaction at standard conditions
Δ_rS°	Entropy of reaction at standard conditions

Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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